Unified Glare Rating

UGR stands for Unified Glare Rating, which measures the glare from lighting installations. It’s a scale defined by the International Commission on Illumination (CIE) to quantify the psychological discomfort caused by glare from luminaires.

How UGR Works:

• UGR values range from 5 (very low glare) to 40 (extremely high glare)
• It considers factors like luminaire luminance, angles, and visual tasks performed within the space
• The calculation involves a precise mathematical formula, taking into account background luminance, average luminaire luminance, solid angle, and displacement from the line of sight

UGR Ratings and Glare Levels:

• UGR ≤ 10: Imperceptible glare, optimal for sensitive environments like healthcare settings or precision workspaces
• UGR 10-16: Low glare, comfortable for general lighting in offices and classrooms
• UGR 16-19: Moderate glare, suitable for office environments, balancing illumination and visual comfort
• UGR 19-22: High glare, may cause discomfort in prolonged exposure, suitable for industrial areas
• UGR > 28: Intolerable glare, typically avoided in indoor settings except for specialized applications like outdoor floodlighting

Importance of UGR:

• Visual comfort: High glare levels can cause discomfort, fatigue, and headaches
• Productivity: Well-designed lighting with controlled glare enhances focus, mood, and overall productivity
• Standards compliance: Many building and lighting standards specify maximum UGR levels for comfortable and safe lighting.¹ ²